The goal of the proposed study is comparative description and analysis of five aspects of crack and other cocaine involvement: (1) initial experimentation patterns, (2) use patterns, (3) overdose experiences, (4) the development of compulsive use, and (5) treatment seeking. Based on preliminary studies that were components of a prior research project, a theory is developed to explain the relationship of these aspects of crack/cocaine involvement to (a) each other -- i.e., using a natural history perspective; (b) the social demographic characteristics of age, ethnicity, and gender; and (c) a complex of five interrelated context variables: (1) the operation of crack and cocaine distribution businesses, (2) differential crack/cocaine availability within a metropolitan area, (3) the user's prior and subsequent involvement in crime, (4) financial access to crack/cocaine, and (5) peer support for crack/cocaine use. The methodology emphasizes testing propositions derived from this theory, with a secondary component of exploratory analysis in a few selected areas. Most of the hypothesis testing requires new data -- interviews with 700 crack and/or cocaine users, half of them in treatment programs and other half "on the street," not in treatment. Demographic subsample goals are specified to assure a good balance for data analysis in a tri-ethnic (black Hispanic, white) sample that includes both males and females age 12-49 (grouped as 12-17, 18-24, 25+). All interviews are to be done in a major metropolitan area noted as a primary site for cocaine importation. As a supplementary data base to compare crack/cocaine problems with those from other drugs, the design also includes analysis of drug emergency data being collected in the same metropolitan area (Miami) from one of the nation's largest hospital emergency rooms.